Various methods for making foundry molds and cores are known. One preferred group of methods are known as cold box methods since these methods require relatively low curing temperatures for curing the binder resin used to bind together the foundry sand.
A particularly useful cold box method is the so called "Ashland" method. This method consists of mixing a resin which can be polymerized with an amine catalyst, such as triethylamine or dimethylethylamine with foundry sand. After the sand mixture is formed into the desired shape in an enclosed molding cavity, a gas to which the amine has been added is then injected into the molding cavity to cause the sand-resin mixture to harden by polymerization of the resin in the mixture.
While the above method has many advantages such as low cure temperature and fast production rates, the process is not without disadvantages. For example, the amine catalysts have a disagreeable odor and a sufficient level of toxicity so that it is necessary to avoid exposing operating personnel to the vapors. Fire and explosion risks are also significant. In addition proper, complete, and efficient distribution of the curing agent is frequently difficult to obtain.
Many catalyst systems now available operate by introducing a liquid phase catalyst into a carrier gas stream, either by bubbling the carrier gas through a tank of liquid, or by injecting the liquid directly into a carrier gas stream. Problems associated with these systems include lack of control over catalyst concentration in the carrier gas, and the likelihood of introducing the catalyst into the curable mixture as a mist or fog. Varying catalyst concentration results in uneconomical processing, since the gassing portion of the cure cycle must be established by the lowest concentration expected. Gassing with higher concentration than necessary merely wastes catalyst and carrier gas. In addition, admission of catalyst as a fog or mist into contact with the formed curable mixture causes the need for longer purge times and also hinders complete penetration and uniform cure of the formed sand-binder mixture. In addition, the presence of liquid phase catalyst which may collect in the delivery system presents numerous problems.